The present invention concerns a method of forming a thin film and a thin film device and it, particularly,relates to a method of forming a thin film which is suitable to the sputtering formation of a wiring layer in a semiconductor device.
For instance for the formation of the thin film of a refractory metal, sputtering of tantalum (hereinafter referred to as Ta) has been introduce in, Journal of Applied Physics, 36 (1965), pages 237-242, and it is disclosed that bias sputtering is effective for reducing the resistance value of the film. Further, sputtering for tungsten (hereinafter referred to as W), has been shown in Applied Surface Science, 38 (1989), pp 295-303 and it is reported that stresses in the film can be suppressed by forming the film under the application of a negative bias voltage and low target power. On the other hand, it is considered that life of the wiring film of the semiconductor device depends on the disconnection of wiring caused by a phenomenon that atoms migrate by the flow of an electric current in the wiring (electromigration) and a phenomenon that the atoms migrate caused by the stresses on the wiring (stressmigration). For the formation of the wiring film of the semiconductor device, it has heretofore been proposed in, for example, Japanese Patent Publication Sho 55-31619, a laminate wiring structure has been proposed with an aim of improving the wiring life and it is described that the structure can suppress the migration of atoms constituting the wiring and the improvement of the wiring life can be realized. Further, it is disclosed in Japanese Patent Laid-Open Sho 60-206045 that electromigration tolerance can be improved by controlling the grain size of the wiring film, which contributes to the improvement of the wiring life. However, although it has been disclosed that the bias sputtering for Ta is effective for reducing the resistance value of the film in the Journal of Applied Physics, 36 (1965), pp 237-242, the stresses in the film are increased by mere application of the bias voltage and it is difficult to obtain a thin film with a less stress and low resistance.
Further, it has been disclosed that if the film is formed with a decreased target electric power, the film stress can be suppressed in the bias sputtering for W, in Applied Surface Science, 38 (1989), pp 295-303, but if the target electric power is decreased, it results in a problem of lowering the deposition rate, as well as it is also difficult to obtain a thin film with less stress and low resistance by the mere application of the bias voltage as described above.
Further, it is described that a wiring having an electromigration tolerance can be provided by using a laminate wiring of a compound layer of aluminum (hereinafter referred to as Al) and a transition metal and Al in Japanese Patent Publication Sho 55-31619 and it is stated that the grain size of Al has to be refined in order to rapidly form the compound layer of Al and the transition metal. However, it has been considered at present that the electromigration tolerance is low if the crystal grain size is fine and it is difficult to obtain a practical reliability in a so-called submicron wiring with the width of a wiring of less than 1 .mu.m by this method.
Further, in Japanese Patent Laid-Open Sho 60-206045, it is described that disconnection failure can be reduced for the wiring in a semiconductor device by controlling the crystal grain of an Al alloy constituting the wiring. However, in the so-called submicron wiring with a wiring of less than 1 .mu.m width, it is difficult to obtain a practical reliability of the wiring by merely controlling the crystal grain size so long as the Al alloy is used in a single layer.